There are currently three accountability structures in place to hold ICANN to account. The first, and perhaps least understood, is that worldwide participation in the naming system, managed by ICANN, is voluntary and subject to modification (as the Chinese have done). If the global community truly became dissatisfied with ICANN, a new root could be developed that everyone referenced instead of the one managed by ICANN ... the ultimate mechanism of accountability... (source: Jonathan Zuck*, emphasis added)*From the testimony of Jonathan Zuck, President, ACT | The App Association, before the U.S. Congress, Committee on the Judiciary, Subcommittee on Courts, Intellectual Property and the Internet on Stakeholder Perspectives on ICANN: The .Sucks Domain and Essential Steps to Guarantee Trust and Accountability in the Internet's Operation, May 13, 2015.
The possibility of a new Internet DNS root is, and always will be, the ultimate mechanism of accountability for both ICANN and the IANA functions, regardless of the outcome(s) of any and all ICANN Cross-Community Working Group processes.
Jon Postel even demonstrated to the world one way it could be accomplished in his 1998 "test"--see: The Day Jon Postel Freed The Internet Root From US Government Control.
See also: What Is The US Government's Claim to the Internet Root? and Alternative DNS root .